The invention relates to a throttle valve positioning device having a housing which forms a bearing arrangement for a throttle valve shaft and comprises a throttle body in which a throttle valve is pivotable, said throttle valve sitting on the throttle valve shaft, which leads through the shaft passage into the throttle body, the housing being of split design, and the circumference of the throttle valve, at least on one side, lying next to the throttle valve shaft at a distance from a passage of the throttle valve shaft in the throttle body.
In the hitherto known arrangements of throttle valves in the throttle body which sit centrally on the throttle valve shaft or in a slot in the throttle valve shaft, leakage air usually cannot be prevented from flowing past in the region between throttle valve shaft, throttle valve and throttle housing and also via the shaft apertures in the bearings. The avoidance of leakage air is made more difficult in particular in split housings having two housing shells, since the parting line of the two housing halves likewise lies in the region of the throttle valve, so that, on account of the very high vacuum produced in the region of the throttle valve, leakage air is drawn in in this region, which can scarcely be sealed off completely.
It has been attempted hitherto to reduce this problem by minimizing the shaft apertures and the mismatch in mold between the housing halves, it not being possible in this way to absolutely remove the problem, but rather it only being possible to provide for a certain improvement with regard to leakage air at increased production costs.
Throttle valve positioning devices of the type described at the beginning have been disclosed by U.S. Pat. No. 1,671,069, U.S. Pat. No. 3,556,475, U.S. Pat. No. 2,934,312 and U.S. Pat. No. 3,260,502.